The Science of Nitrite High levels of nitrite quickly lead to fish death. Even trace amounts of nitrite stress fish, suppressing their immune system and, thereby, increase the likelihood of disease and subsequent fish loss.Nitrite is produced by the biological filter. Beneficial bacteria in the biological filter convert toxic ammonia into toxic Nitrite (NO2-). The biological filter then converts nitrite into less-toxic nitrate (NO3-). If not removed, nitrite will prevent fish from carrying on normal respiration. In a new freshwater aquarium, the nitrite level may surge to 10 ppm (mg/L) or more, and then fall rapidly as the biological filter becomes established. The nitrite will be converted to nitrate. This process may take several weeks. In an established aquarium, the nitrite level should always remain at 0 ppm (mg/L). The presence of nitrite indicates possible over-feeding, too many fish, or inadequate biological filtration |